I kinda think it would be nice to receive an email or a notification inside the forum if one receives merit
But why? Your Merit total is shown right under your username. All you need to do is remember the last number, and click your username > Merit > loooooooong
* scroll down to see where it came from.
I've done this for every Merit I ever received, and I don't think an email is going to make that less work.
You can of course use a generic page-change-notification service on the Merit counter in your profile. That service will regularly check it for you, and send you an email every time it changes.
*Just Merit source problems